1. Field of the Invention
The disclosure herein relates generally to determining analyte concentrations within a material sample.
2. Description of the Related Art
Millions of diabetics are forced to draw blood on a daily basis to determine their blood glucose levels. In addition, the detection of other blood constituents, such as the determination of the concentration of alcohol in the bloodstream, often requires blood withdrawal in order to perform a precise analysis thereof. A search for a noninvasive methodology to accurately determine blood constituent levels has been substantially expanded in order to alleviate the discomfort of these individuals. A significant advance in the state of the art of noninvasive blood constituent analysis has been realized by the development of spectrometers, including xe2x80x9cthermal gradientxe2x80x9d spectrometers, which analyze the absorbance of particular wavelengths of infrared energy passed through and/or emitted by a sample of tissue. These spectroscopic analytical devices typically employ a window or lens for admitting infrared spectra into the device for analysis by infrared detectors.
Although these devices have marked a significant advance in the state of the art of noninvasive blood constituent analysis, further improvements could be made in the performance and ease of manufacture of such devices.
A device and method for determining analyte concentrations within a material sample are provided. A modulating temperature gradient is induced in the sample and resultant, emitted infrared radiation is measured at selected analyte absorbance peaks and reference wavelengths. The modulating temperature gradient is controlled by a surface temperature modulation. One embodiment provides a transfer function relating the surface temperature modulation to a modulation of the measured infrared radiation. Phase and magnitude differences in the transfer function are detected in the presence of the sought-after analyte. These phase and magnitude differences, having a relationship to analyte concentration, are measured, correlated and processed to determine analyte concentration in the material sample. Another embodiment provides a method for transforming thermal phase spectra to absorption spectra for consistent determination of analyte concentration within the sample.
In one embodiment, a method is provided for determining a concentration of an analyte within a material sample. The material sample is induced to emit electromagnetic energy in a time-varying manner. The induced electromagnetic energy emitted by the material sample is measured at at least one wavelength, wherein the measuring comprises analyzing the material sample with an optical measurement system. A phase of the electromagnetic energy is determined and then converted into an absorption value. The concentration of the analyte is then determined based at least in part on the absorption value.
In another embodiment, a method is provided for determining a concentration of an analyte within a material sample. At least a portion of a phase spectrum is determined based on electromagnetic energy emitted by the material sample. The at least a portion of the phase spectrum is converted into at least a portion of an absorption spectrum. The concentration is determined based on the at least a portion of the absorption spectrum.
In one embodiment, an analyte detection system is provided. The analyte detection system comprises a detector array, a processing circuit in communication with the detector array, and a module. The module is executable by the processing circuit whereby the processing circuit converts a phase spectrum, based on electromagnetic energy emitted by a material sample and measured by the detector array, into an absorption spectrum and determines a concentration of an analyte within the material sample based on the absorption spectrum.
In another embodiment, a method of estimating analyte concentration in a sample is provided. A time varying temperature is applied to a portion of a sample. Time varying infrared radiation intensity received from the sample is measured in at least one wavelength band. An absorption coefficient a is calculated in the wavelength band based at least in part on the time varying infrared radiation intensity received from the sample.